Pyrotechnical cutting apparatus



Aug. 5, 1952 J. DUMAS I PYROTECHNICAL CUTTING APPARATUS Filed 001;. 50, 1946 JACQUES DUMAS vENToiZ (5, MM.

8 ATT Y Patented Aug. 5, 1952 rrno'racnmcan CUTTING APPARATUS Jacques Dumas, Paris, France, assignor to Societe.

Industrielle dEntreprise et de Mecanigue, Paris, France, a French company ApplicationOctober 30, 1946, Serial No. 706,639 In France November 7, 1945 1 Claim. 1

The present invention has for its object a pyrotechnical apparatus specially adapted for pyrotechnical cutting-as. it is practiced in the enterprises of civil engineering and public works, by the apposition of a longitudinal set of explosives to the surface or wall to be out.

Its particular object is to provide structures of cutting apparatus which will ensure an efficient cutting, superior to that of the usual practice, while at thesame time only employing a much smaller quantity of explosive.

Devices according to the invention comprise an elongated cavity, provided in the explosive, according to a course orientated in the direction of propagation of the detonation wave within the explosive or in a neighboring direction, and opening on the side of the wall to be cut.

The provision of such a cavity, preferably extended on the total length of the apparatus, permits the utilization ofthe well-known effect of the hollow charge, by thus creating a plane of concentration of the effect of the cutting and,

thereby, notably reducing the quantity of explosive used. The cutting effect is, besides, reinforced by the lining of said cavity with a wall made of metal or of a cast or agglomerate material, of a strong mechanical resistance, applied either directly on the surface of the explosive, or on an intermediate envelope containing said explosive. I

The cross section of said cavity, substantially symmetrical with reference to a plane perpendicular to the plane of the surface to be cut, in other words, to the plane defined by its opening along the longitudinal section of the useful charge of the explosive (the section below which the concentration action of the detonation is no longer directed towards the surface to be out), can be either of any triangular, polygonal, or ourvilinear shape desired, but, in accordance with another feature. of the invention, when working with explosives having a high speed of detonation, this cross-section is so designed that the isosceles triangle inscribed, having for its apex the point of the normal maximum distance to the aforesaid plane of opening and for its base, the distance between the extreme points of application of the useful explosive charge in this section shows an angle at the apex Of between 90 and 120.

According to another feature of the invention, the outer casing of the device, if rigid, or the lining of the cavity, is lengthened by construction in the direction of the surface to be cut, in such a manner as to ensure, when the apparatus is put into place, a distance to said surface corresponding to the optimum efiiciency of the cutting charge employed; said distance being always less than about one and a half times the opening of the cavity. g,

According to another feature of the invention, in order to obtain a higher efficiency from the cutting apparatus on awkward or irregular surfaces, the structures of. the apparatus are made flexible or plastic longitudinally, while, at the same time, retaining practically the above men-.

tioned dimensioning of their cavities.

These features, as well as many others, will'be explained in fuller detail in the following description given in relation to the annexed drawings in which:

Fig. 1 shows, in perspective, a diagrammatical example of embodiment of such an apparatus;

Figs. 2 and 3 and Fig. 5 givein cross-section, two alternatives of the example shown in Fig. 1.

Fig. 4 shows the limit of dimensioning provided for the cross-section of the cavity; and 7 Figs. 6 to 9 represent various alternatives of embodiment, incorporating some structural features specially designed to give a simple method of putting the invention into execution.

It can be seen, by referring to Fig. 1, that a cutting apparatus incorporating certain features of the invention comprises an elongated charge of explosive l associated at one of its ends to a priming charge at the end 2, and in which is made a longitudinal cavity 3 limited by a lining 4 which is relatively thin in order to be relatively flexible but possesses a certain mechanical resistance, for example, made of metal or of a cast or agglomerated material. This casing is lengthened by walls such as 5 and 6 which permit of obtaining by construction the optimum distance of action between the useful plane of the explosive charge and the planeof the surface to be out which distance is variable following the shape and nature of the charge I and the material of the surface to be cut, but which is less than one and a half times the transversalwidth of the cavity formed by said walls. Besides, in another mannenwithout leaving the domain ofinthat is to say, in section, the

' on Fig. 2 in order to form of cavities described above, one or several 3 ven-tion, this distance can be defined'during the manufacturing process, not being calculated from the rigid lining of the cavity 3, but from the rigid casing surrounding the explosive charge.

The expression useful plane of the explosive charge which has been used, applies to the fictitious plane defined by the lines according to which the explosive charge is joined to the covering of the cavity (lines BB and CC on Figure 1). It can, in fact, be understood that the arrangement of the explosive charge I around the cavity 3 should be made in such a manner that it ensures a concentration of the detonation waves in the direction of the obstacle and that the presence of explosive outside of the opening BC of the cavity would cause the consumption of an additional quantity of explosive which would be useless if not even harmful.

The cross-section of the cavity 3 plays an important part regarding the efficiency of the device and this will now be shown. On Fig. 1 this crosssection is shown as an isosceles triangle with its apex upper A and laterals B and C. This triangular section .is not necessary, however, and

the walls AB and BC. do not even need to be flat, linesAB and BC of the casing may be curved as shown, for'example an ogivel of apex A or even a semi-circular arch as is shown as an illustration in 8 of Fig. 3, where the section is a semi-circle with the diameter BC. Broadly, for high speed detonation explosives, the crosssection of the cavity which should preferably be symmetrical with respect to th longitudinal plane of the apparatus, should have such aform that the above-mentioned isosceles triangle with its points AB and C defined above,

presents at its apex A an angle of about'90" to 120. Fig. 4 I

shows these angles and the corresponding limits of openings BC and B1 and C1 for the same height AH; the walls of this cavity can then have any desired form, from the dihedral shape BAC to the cylindrical shape B1AC1, passing through any other curvilinear and (or) polygonal shape. The

efficiency of the apparatus is reduced both above and below these sections, owing to the badutilization of the explosive. J

In order to reinforce the directional effect, and,

i in consequence, the destructive eifect, it has also to the general shape longitudinal outwardly directedgrooves as shown for been provided for to adjoin example in 9 on Fig. 5.-

It is clear that the structures described above lend themselves to numerous ways of embodying same especially with regard to the nature of the explosive to be used, without leaving the scope of the invention. However, a special feature relating to the manufacture of this apparatus, consists of arranging for its construction in the form of two .tubes, one of which runs into the other,

in such a manner as to join their walls to a portionlof their respective sections, the explosive being poured or pressed between these tubes. By tubes it is understood not only circular tubes but thoseof all forms of circular, elliptical, oval, or polygonal sections as desired. It is thus that in the, example shown in Fig. 6 the explosive I oocupies the space between an oval tube II which forms at the same time the outer casing and a tube of circular section I 2 which forms the wall of the cavity 3. In the example shown in Fig. 7 the outside tube I3is flattened at I4 in order to constitute a supporting wall on the surface to be cut, the cavity 3 being limited by a profiled element I5 having a V-shaped cross section. This element I5 is wedged in the tube I3 by the compressed powder behind it. In the example given, Fig. 8, the external casing I6 is made of a flexible sheath which is fixed around the tube I'I, limiting the cavity 3 and the explosive I, and holding them in their relative desirable positions. Structures of this type are specially interesting, from the sole point of view of efficiency, for the underwater employment of the cutting apparatus; in fact, it has been discovered that in the latter case it was necessary to keep the cavity 3 watertight, which was rendered easy to realize, owing to these shapes.

In addition, this method of realization permits the simplification of putting into practice another feature of the invention, that of making flexible the cutting apparatus comprising a cavity in order to facilitate putting them into position and to increase their efliciency on curved or irregular surfaces. It is suflicient, in fact, to provide for flexible tubes, water-tight or not, and other flexible elements of any known convenient type, and to employ either a pulverulent or a plastic explosive, while keeping, at the same time, the degree of rigidity desirable for the wall of the cavity 3, and the extensions of this wall,-or of the casing, used to keep the required spacing between the cutting apparatus and the surface to be cut, for example, by making them of a plastic, moulded, 0r agglomerated material reinforced or not by a casing or by a metallic framework.

For instance in Fig. 1 the charge I will be plastic, whereas the lining 4 and the walls 5, 6 thereof will be flexible.

In Fig. 6, the charge I may be pulverulent or plastic, the tubes II and I2 being flexible.

Instead of making the cutting apparatus relatively flexible along the whole of its length, it is also provided to construct them of rigid elements, short in length but jointed between each other. Fig. 9 shows diagrammatically, such an arrangement in which the rigid elements IB, I9, 20 of a cross-section such as is shown in relation to Figs. 1 to 8, or derived from these examples, are provided with terminal faces 2i and 22, convex and concave respectively, which fitinto each other. The continuity of the whole is ensured for example, by a flexible sheath 23, or it can simply be realized by placing some elements, one after the other onto the cutting wall.

It is clear that the invention is not limited to the examples of realization shown and described, but is, on the contrary, capable of numerous alternatives and adaptations without leaving its scope.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

In a blasting and cutting device, an elongated explosive charge formed of a plurality of comparatively rigid units and a relatively flexible sheath encasing all said units, the contacting adjacent ends of said units being formed respectively concavely and convexly and having substantially identical radii, whereby flexing of said sheath will maintain a substantially unaltered area of contact between adjacent ones of said units, said charge being formed with a longitudinal groove along the entire length thereof, so as to concentrate the cutting effect of the charge when exploded.

JACQUES DUMAS.

(References on following page) 5 REFERENCES CITED FOREIGN PATENTS The following references are of record in the Number Country Date file of this patent: 28,030 Great Britain of 1911 UNITED STATES PATENTS 5 OTHER REFERENCES Number Name Date Zeitschrift fiir das Gesamte Schiess und 1,440,601 Holran Jan. 2, 1923 Sprengstofiwesen, May 15, 1914, pp. 183-187. 5 Ha is et al- M 31, 1 The Hollow Charge, in The Illustrated Lon- 2,404,440 Holm July 23, 1946 don News, November 25, 1944, pp. 604, 605. 2,407,093 Mohaupt -1 Sept. 3, 1946 10 The Explosive Engineer, July-August 1945, pp. 2,409,848 Greulich Oct. 22, 1946 160-163.

2,543,057 Porter Feb. 2'7, 1951 

